Renal Approach to Proteinuria and Polyuria

Question 1

What are the 3 layers of the glomerular filtration barrier?

Answer 1

Fenestrated capillary endothelium, glomerular basement membrane, and podocytes

Question 2

What is the function of the fenestrated capillary endothelium?

Answer 2

Keeps out cells

Question 3

What is the function of the GBM?

Answer 3

Keeps out large plasma proteins (i.e. albumin)

Question 4

What is the function of podocytes?

Answer 4

Keeps out large plasma proteins (such as albumin)

Question 5

What can get through the glomerular filtration barrier?

Answer 5

Low molecular weight proteins (beta-2 macro globulin, light chains) that are filtered and reabsorbed in the proximal tubule; solutes and small molecules (Na, K, glucose)

Question 6

What amount of protein in the urine is normal?

Answer 6

A small amount of protein in the urine is normal; mostly made up low molecular weight proteins that pass through the glomerular filtration barrier; also includes Tamm-Horsfall protein produced by the renal tubule

Question 7

What is the normal daily protein excretion?

Answer 7

<150mg/day

Question 8

What is the normal albumin daily excretion?

Answer 8

<30mg/day

Question 9

What are the 3 types of proteinuria?

Answer 9

Glomerular, overflow, tubulointerstitial

Question 10

What is glomerular proteinuria?

Answer 10

Damaged glomerular filtration barrier –> albuminuria; nephrotic and nephritic syndromes

Question 11

What is overflow proteinuria?

Answer 11

Filtered LMW protein load exceeds reabsorptive capacity of kidney (ex. light chains due to multiple myeloma)

Question 12

What is tubulointerstitial proteinuria?

Answer 12

Tubular damage –> impaired reabsorption of LMW proteins (ex. ATN)

Question 13

What are the pros for a urinalysis?

Answer 13

Cheap and easy, can detect other urine abnormalities

Question 14

What are the cons for urinalysis?

Answer 14

Only detects albumin, low sensitivity (only detects >300mg protein)

Question 15

What are the pros for spot urine albumin/Cr ratio?

Answer 15

Can detect small amounts of albumin (important in recognizing early diabetic nephropathy)

Question 16

What are the cons for spot urine albumin/Cr ratio?

Answer 16

Only detects albumin

Question 17

What are the pros for spot urine protein/Cr ratio?

Answer 17

Detects all proteins (albumin, light chains, beta 2 macro globulin)

Question 18

What are the cons for spot urine protein/Cr ratio?

Answer 18

Not as well validated in diabetic nephropathy

Question 19

What are the pros for 24 hour urine protein?

Answer 19

Gold standard

Question 20

What are the cons for 24 hour urine protein?

Answer 20

Inconvenient

Question 21

With light chain nephropathy (due to multiple myeloma), UA and spot urine albumin/Cr ratio may falsely show what?

Answer 21

No protein; need spot urine protein/Cr ratio to detect light chain proteinuria

Question 22

What are the pulmonary-renal syndromes?

Answer 22

Anti-GBM and ANCA associated (GPA, microscopic polyangitis, eosinophilic granulomatosis with polyangitis)

Question 23

All pulmonary-renal syndromes can present with what?

Answer 23

rapidly progressive glomerulonephritis

Question 24

What is the urinary pattern for nephritic syndromes?

Answer 24

Proteinuria (<3.5g/day), hematuria, dysmorphic RBC and RBC casts

Question 25

What is the urinary pattern for nephrotic syndrome?

Answer 25

Heavy proteinuria (>3.5g/day), fatty casts, oval fat bodies, minimal hematuria

Question 26

What is polyuria?

Answer 26

production of >3L of urine in 24 hours

Question 27

What is urinary frequency?

Answer 27

Increase in frequency of urination, regardless of volume voided

Question 28

What is nocturia?

Answer 28

increase in frequency of urination at night

Question 29

Does diabetes insipidous cause hypernatremia?

Answer 29

If thirst mechanism intact, often not (Na will typically be upper end of normal, pt compensates for ADH inactivity by drinking more water); if thirst mechanism lost or pt lacks access to water can see hypernatremia